U.S. patent number 11,004,636 [Application Number 16/169,496] was granted by the patent office on 2021-05-11 for electrical relay with mounting bracket.
This patent grant is currently assigned to Albright International Limited. The grantee listed for this patent is Albright International Limited. Invention is credited to Michael Sheridan.
United States Patent |
11,004,636 |
Sheridan |
May 11, 2021 |
Electrical relay with mounting bracket
Abstract
The present invention relates to the field of electrical relays.
In particular the invention relates to a bracket a relay and
bracket combination which permits the relay to be mounted on a
surface or panel in a plurality of angular rotational orientations.
There is provided a relay and mounting bracket combination
comprising a relay having a body with a terminal end portion
provided with one or more electrical terminal connectors and a base
end portion adapted for engagement with the bracket, wherein the
bracket is provided with attachment features which facilitate the
mounting of the bracket to an external object or surface when the
bracket is engaged with the base end portion of the relay.
Inventors: |
Sheridan; Michael (Whitchurch,
GB) |
Applicant: |
Name |
City |
State |
Country |
Type |
Albright International Limited |
Whitchurch |
N/A |
GB |
|
|
Assignee: |
Albright International Limited
(Whitechurch, GB)
|
Family
ID: |
60481688 |
Appl.
No.: |
16/169,496 |
Filed: |
October 24, 2018 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190122843 A1 |
Apr 25, 2019 |
|
Foreign Application Priority Data
|
|
|
|
|
Oct 25, 2017 [GB] |
|
|
1717557 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01H
45/04 (20130101); H01H 51/281 (20130101); H01H
50/047 (20130101); H01H 11/0031 (20130101); H01H
50/045 (20130101) |
Current International
Class: |
H01H
45/00 (20060101); H01H 45/04 (20060101); H01H
50/04 (20060101); H01H 51/28 (20060101); H01H
11/00 (20060101) |
Field of
Search: |
;335/202 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Talpalatski; Alexander
Attorney, Agent or Firm: Stoel Rives LLP
Claims
The invention claimed is:
1. A relay and mounting bracket combination comprising a relay
having a body with longitudinal axis defined between a terminal end
portion provided with one or more electrical terminal connectors
and a base end portion adapted for engagement with the bracket,
wherein the bracket is provided with one or more attachment
features which facilitate the mounting of the bracket to an
external object or surface when the bracket is engaged with the
base end portion of the relay, wherein the engagement between the
base end portion and the bracket is made by the inter-engagement of
one or more protruding nubs with one or more constraint features
thereby providing axial constraint against withdrawing of the base
end portion from engagement with the bracket, said one or more nubs
and one or more constraint features being configured so as to be
capable of co-operating at any one of a plurality of rotational
orientations of the base end portion with respect to the bracket,
whereby the relay may be mounted on the bracket in a selected one
of a plurality of rotational orientations.
2. A combination as claimed in claim 1 wherein the bracket is
provided with a generally annular aperture or seat sized to
accommodate the base end portion therein, which aperture or seat is
provided with said one or more constraint feature.
3. A combination as claimed in claim 2 wherein said one or more
protruding nubs are radially extending from the base end
portion.
4. A combination as claimed in claim 2 wherein the constraint
feature comprises an annular lip or shoulder provided on or in the
annular aperture or seat of the bracket, and said one or more nubs
are provided projecting radially outward from the base end portion
of the relay with the lip or shoulder providing constraint against
axial displacement the nub or nubs through a continuous range of
relay body rotational positions with respect to the bracket.
5. A combination as claimed in claim 4 wherein at least a portion
of the nub-facing side of the lip or shoulder is provided with a
surface treatment which promotes mechanical keying of the nub or
nubs with the lip or shoulder, such as surface roughening or
texturing or saw tooth profiling.
6. A combination as claimed in claim 2 wherein the constraint
features comprise a series of circumferentially spaced-apart
discrete recesses formed on an inside wall of the bracket aperture
or seat, the engagement of a nub and a recess providing constraint
against axial movement of the nub, each recess corresponding to a
discrete rotational position of the relay body with respect to the
bracket.
7. A combination as claimed in claim 6 wherein each recess
comprises a roof portion which provides axial constraint, side
walls which provide rotational constraint and an open base portion
which permits entry of the nub into the recess.
8. A combination as claimed in claim 6 wherein the nub is sized and
configured to be a sliding fit in each recess.
9. A combination as claimed in claim 1 wherein the one or more nubs
have an axial height which is greater than an axial space provided
between the constraint feature or features and a surface to which
the bracket is to be mounted so that when the bracket is placed
base edge-on to the surface and fixed with the base edge flush to
the surface a nub in the constraint feature will be axially
compressed.
10. A combination as claimed in claim 1 wherein one or more open
slots are provided for said one or more nubs to bypass the
constraint feature or features when rotationally aligned with an
open slot, after which the nub may be rotationally displaced so as
to become aligned with a position in which the nub can be axially
constrained by the constraint feature.
11. A combination as claimed in claim 2 wherein the bracket is a
generally annular member having an inside surface which defines the
aforementioned annular aperture, said one or more open slots are
provided in said inside surface, and said one or more nubs are
provided projecting radially outwardly from the base end portion of
the relay.
12. A combination as claimed in claim 11 wherein there are two
slots and two corresponding nubs.
13. A combination as claimed in claim 2 wherein the base end
portion of the relay body is generally cylindrical and sized to be
a sliding fit in the annular aperture.
14. A combination as claimed in claim 13 wherein the constraint
feature or features are provided on the inside surface of the
annular aperture.
15. A combination as claimed in claim 14 wherein the bracket is a
unitary member.
16. A combination as claimed in claim 1 wherein the bracket
attachment features comprise two or more radial, outwardly
projecting cheek portions.
17. A combination as claimed in claim 16 wherein each cheek is
provided with a bore in which a screw, bolt or rivet may be
disposed for fixing to an underlying surface.
Description
RELATED APPLICATIONS
This application claims priority to United Kingdom Application No.
1717667.1, filed on Oct. 25, 2017 and titled, "Electrical Relay
with Mounting Bracket," which is hereby incorporated by reference
in its entirety.
TECHNICAL FIELD
The present invention relates to the field of electrical relays
such as heavy-duty relays, also known as contactors. In particular
the invention relates to a relay and mounting bracket combination
which permits the relay to be mounted on a surface or panel in one
of a plurality of angular rotational orientations with respect to
the bracket.
BRIEF DESCRIPTION OF THE DRAWINGS
Following is a description by way of example only and with
reference to the figures of the drawings of modes for putting the
invention into practice. In the figures:
FIG. 1A is a top plan view of a heavy duty relay with a fixed
bracket for panel mounting.
FIG. 1B is a top plan view of a similar relay with a fixed bracket
having an alternative rotational orientation.
FIG. 2A is an isometric three quarter view from above of a relay
and bracket combination in accordance with a first embodiment of
the present invention, the combination in a first
configuration.
FIG. 2B is an isometric three quarter view of the combination of
FIG. 2A in a second configuration.
FIG. 2C is an isometric three quarter view of the combination of
FIG. 2A in a third configuration.
FIG. 3A is a top plan view of the bracket shown in FIG. 2.
FIG. 3B is an underside plan view of the same bracket.
FIG. 4 is a top plan schematic view of a relay and bracket
combination in accordance with the present invention.
FIG. 5 is an underside view of a bracket used in a bracket and
relay combination in accordance with a second embodiment of the
invention, showing the location of nubs carried by a relay body
(not shown), along with a magnified portion showing the detail of
the bracket.
FIG. 6A is part side view of a relay used in the second
embodiment.
FIG. 6B is a part cross-sectional side view through the plane
represented by the line A-A' in FIG. 5.
DETAILED DESCRIPTION
Devices such as contactors or heavy duty relays generally have
mounting brackets or mounting holes the position of which is fixed
in relation to other important features of the device such as the
main terminals or coil terminals. Two examples of relays having
fixed bracket orientations (90 degrees rotational variation) are
shown in FIGS. 1A and 1B. Of course the fixed positions of the
bracket mounting holes with respect to the terminal locations or
orientations do not always suit the layout of the panel or
represent the best orientation for the device's terminals to be
connected with external electrical connectors in a circuit. This
can be a problem if, for example, the brackets have been pre-bored,
or pre-bored with insufficient precision, or if there is
insufficient space for alternative bore orientations to be
formed.
One solution is to make several variants of the relay brackets with
each having a different relay orientation, but this is expensive
and requires stockists or installers to maintain a range of
brackets. Alternatively a bracket with multiple attachment bores
(i.e. having a large amount of rotational symmetry) could be made,
but this may render the bracket too bulky to fit in spatially
constrained locations.
The present invention seeks to provide a relay and mounting bracket
combination which permits an installer to select one of a range of
relay rotational orientations with respect to the associated
mounting bracket, but without the aforementioned cost and bulk
compromises.
According to one aspect of the invention there is provided a relay
and mounting bracket combination comprising a relay having a body
with a longitudinal axis defined between a terminal end portion
provided with one or more electrical terminal connectors and a base
end portion adapted for engagement with the bracket, wherein the
bracket is provided with one or more attachment features which
facilitate the mounting of the bracket to an external object or
surface when the bracket is engaged with the base end portion of
the relay.
The engagement between the base end portion and the bracket is made
by the inter-engagement of one or more protruding nubs with one or
more constraint features thereby providing axial constraint against
withdrawing of the base end portion from engagement with the
bracket, said one or more nubs and one or more constraint features
being configured so as to be capable of co-operating at any one of
a plurality of rotational orientations of the base end portion with
respect to the bracket, whereby the relay may be mounted on the
bracket in a selected one of a plurality of rotational
orientations.
The one or more nubs are typically provided on or in the relay base
end portion. The one or more constraint features are typically
provided on or in the mounting bracket.
The bracket may comprise a member which defines a generally
cylindrical aperture or seat sized to accommodate the base end
portion therein. The member is preferably generally annular in
form. The aperture or seat is preferably provided with said one or
more constraint feature, for example on an inner surface of said
seat or aperture.
Said one or more protruding nubs are preferably radially extending
and can be any shape which permits it to snag a counterpart
constraint feature. Said one or more protruding nubs may be
radially extending from the base end portion, for example radially
extending outwardly from an outside surface of the base end
portion.
In a preferred arrangement a constraint feature comprises an
annular lip or shoulder provided on or in the annular aperture or
seat of the bracket. The one or more nubs may be provided
projecting radially outward from the base end portion of the relay.
The lip or shoulder thus provides constraint against axial
displacement of the nub or nubs through a continuous range of relay
body rotational positions with respect to the bracket. Of course
the annular lip or shoulder may be interrupted by one or more
bypass features (such as axial slots) which permit the nub or nubs
to bypass the constraint feature before being rotated and drawn
back into engagement under the lip or against the shoulder.
At least a portion of the nub-facing side of the lip or shoulder
may be provided with a surface treatment which promotes mechanical
keying of the nub and lip or shoulder, such as surface roughening
or texturing, and/or the nub itself may also be provided with a
surface treatment for the same purpose. The surface treatment may
be the provision of inter-engaging surface features, such as saw
tooth profile elements.
In another preferred arrangement the constraint features may
comprise a series of circumferentially spaced-apart discrete
recesses formed on an inside wall of the bracket aperture or seat.
The engagement of a nub and a recess provides constraint against
axial movement of the nub and each recess corresponds to a discrete
rotational position of the relay body with respect to the bracket.
There may be at least four such recesses, preferably at least 8,
and more preferably at least 12.
Each recess typically comprises a roof portion which provides axial
constraint. There may be side walls which provide rotational
constraint, and an open base portion which permits entry of the nub
into the recess.
The nubs are preferably each sized and configured to be a sliding
fit in each recess.
In another aspect of the invention the one or more nubs have an
axial depth which is greater than an axial space provided between
the associated constraint feature and a surface to which the
bracket is to be mounted. Thus when the bracket is placed base
edge-on to the surface and fixed with the base edge flush to the
surface, a nub in the constraint feature will be compressed between
the constraint feature and the flush surface. In this way the nub
or nubs may be clamped tightly against movement.
In yet another aspect of the invention one or more open slots are
provided for the nub or nubs to bypass the constraint feature when
rotationally aligned with the open slot or slots, after which the
nub or nubs may be rotationally displaced (by rotating the relay
with respect to the bracket) so as to become aligned with a
position in which the nub or nubs can be axially constrained by a
constraint feature or features. The relay and bracket are then
moved axially apart so that the nub or nubs enter into the
appropriate constraint feature or features.
The bracket is preferably a generally annular member having an
inside surface which defines the aforementioned annular aperture.
Said one or more open slots may be provided in said inside surface,
and said one or more nubs may be provided projecting radially
outwardly from the base end portion of the relay.
In a preferred arrangement there are two slots and two
corresponding nubs, which slots and nubs may be positioned in a
diametrically opposed configuration.
The base end portion of the relay body may be generally
cylindrical. The body is preferably sized (typically the outside
diameter) to be a sliding fit in the annular aperture. The
constraint feature or features may be provided on the inside
surface of the annular aperture.
The bracket is preferably a unitary member, so as to provide
simplicity and no assembly at the point of installation (other than
engagement with the relay).
The bracket attachment features may comprise two or more radial,
outwardly projecting cheek portions. Each cheek may be provided
with a bore in which a screw, bolt or rivet may be disposed for
fixing to an underlying surface. Other fixing means may be utilized
such as gluing, or brazing or spot or pressure welding, in which
case a bore may not be needed.
In a further aspect of the invention there is provided a
combination of a relay and mounting bracket comprising a relay
having a body with a terminal end portion provided with one or more
electrical terminal connectors and a base end portion adapted for
engagement with the bracket, wherein the bracket is provided with
one or more attachment features which facilitate the mounting of
the bracket to an external object or surface when the bracket is
engaged with the base end portion of the relay, wherein an
engagement between the base end portion and the bracket is made by
the co-operation of one or more protruding nubs with one or more
constraint features which provide axial constraint against
withdrawing of the base end portion from the bracket aperture or
seat, wherein the bracket comprises a generally annular member
which defines a cylindrical aperture or seat sized to accommodate
the base end portion therein, and wherein the body portion is
provided with said one or more protruding nub or nubs are radially
extending and are each radially oversized with respect to the
radius of the bracket aperture or seat, the aperture or seat having
an inside surface provided with one or more axially extending open
bypass slots each capable of receiving an oversized nub when
circumferentially aligned therewith, so that the base end portion
may axially enter the bracket aperture or recess with the nubs
passing through the slots, and wherein said inside surface of the
aperture or recess is further provided with one or more inwardly
directed shoulder features, sized to accommodate the nub or nubs
therein but providing axial constraint which prevents axial
withdrawal of the nub or nubs when the shoulder feature covers the
nub, the arrangement being such that the relay base portion may be
engaged with the bracket by aligning the nub or nubs with the axial
slots, and then twisting the bracket with respect to the base
portion so that the nub or nubs are accommodated in a shoulder
feature or features, which shoulder feature or features prevent
axial disengagement of the base portion from the bracket by acting
upon the nub or nubs.
Each nub may have any shape capable of snagging a constraint
feature, but each preferably has the form of a generally
rectilinear section block having the form of annular sector. Each
recess for constraining the nub preferably has the form of an
annular sector cut-out in the aperture inside surface.
The terminal end portion of the relay is in certain embodiments
typically too large to be passed through the bracket aperture, so
that the bracket cannot pass beyond the terminal end portion. This
means that the bracket can only be engaged with the relay base
portion after passing the base portion and being drawn back onto
the base portion and its associated nub or nubs.
In FIG. 1A a heavy duty relay (also known as a contactor) is shown
generally as 1. The relay comprises a generally cylindrical body
portion 2 having a top face 3 which is provided with two upstanding
diametrically spaced apart screw threaded main terminals 4,5 each
provided with a nut and spring washer. A central upstanding fin 6
is disposed equidistant between the main terminals (a similar
arrangement is shown in FIG. 2). A pair of electromagnetic coil
terminals 9 (for activating the device) are upstanding from one
side of the top face. A base region of the device is provided with
a fixed mounting bracket which includes two diametrically opposed
cheek portions 7,8. The cheek portions are each provided with a
vertical mounting bore. The device may be attached to an underlying
panel (or some other mounting location) by means of screws or bolts
or rivets or the like (not shown). A variant of the device is shown
in FIG. 1B in which the fixed mounting bracket has an orientation
90 degrees offset as compared to the device of FIG. 1B.
First Embodiment
A first embodiment of a combination heavy duty relay 10 and a
mounting bracket 11 is shown in FIG. 2. The relay 10 has a
cylindrical body portion 12. The cylindrical body portion has a
base region 13 provided with two diametrically opposed nubs in the
form of square section, curved sector blocks 14 (only one visible
in FIG. 2). projecting radially from the body portion surface.
There is a cylindrical upper body portion 20 which is provided with
two upstanding screw threaded main terminals 24, 25 which are
provided with associated mounting nuts and spring washers. There is
a central upstanding fin 26 to prevent shorting of terminal
contacts between the terminals. The upper body portion in this
embodiment is larger in diameter than the body portion 13 below, so
a shoulder 22 is formed at the junction of the two portions.
A mounting bracket is a unitary cast or moulded generally annular
member 27 which is formed with diametrically opposed cheek portions
23, each with a bore 30 best seen in FIGS. 3A and 3B. The annular
member has an inside cylindrical surface 28 which is sized to
provide a sliding fit for the body portion 12 of the relay. The
shoulder 22 prevents the relay from falling through the bracket.
The inside surface 28 is formed with a series of downward opening
inset recesses or pockets 15 (see also FIG. 3B), each having a
rectilinear circular sector form which is sized to match and
accommodate blocks 14 therein. The inside surface is also formed
with two diametrically opposed bypass slots 17 (see FIG. 3A) which
are recessed into the member surface and are open at both ends.
These slots 17 are sized and disposed so as to align and co-operate
with the blocks 14 when the bracket and relay are manipulated into
a bypass orientation. In this orientation the bracket 27 may be
slipped onto the base region 13 of the relay body, with the blocks
passing through the bypass slots 17 as shown in FIG. 2A until the
bracket is sits around the body portion 12, per FIG. 2B. The
bracket is then free to be rotated with respect to the body
portion. Once a desired orientation has been achieved, the bracket
may be axially displaced downwards so that the blocks 14 enter the
(closest) aligned recesses 15 and engage therewith, as shown in the
cutaway view of FIG. 2C. The bracket is then fixed against rotation
with respect to the relay body. When the mounting bracket is fixed
to an underlying surface and bolted, riveted or screwed into place
the relay is securely retained in the selected orientation. By
tailoring the tolerances between blocks 14 and recesses 15 a close,
wobble-free sliding or interference fit can be obtained. In one
example the blocks 14 are slightly axially taller than the recesses
15, so that when the mounting bracket is secured flush to a flat
substrate via the cheek bores, the bracket urges onto a top surface
of the blocks so as to hold the relay securely and tightly.
In this way the bracket orientation can be tailored to a desired
one of a range of possible positions corresponding to recess and
block pair engagements, as shown in FIG. 4 in which four possible
orientations are shown (although more orientations may be available
depending upon the number of recess pairs).
Second Embodiment
In this embodiment an alternative bracket (FIG. 5) is used in the
combination of mounting bracket and relay. The relay (not shown in
FIG. 5) is unchanged and has two nubs (shown as blocks) the
position and profile of which is shown at 14. These blocks are
radially projecting, as shown in FIG. 6. However, in this
embodiment, the inside surface 28 of the bracket member is formed
with a continuous annular recess 31 (rather than a series of
discrete recess pockets) at a lower end region of the inside
surface of the bracket member. This forms an annular shoulder 29
shown in FIG. 6. The pair of axial bypass slots 17 remain and
interrupt the annular shoulder at two diametrically opposed
locations.
This arrangement operates in a similar way as the first embodiment,
with a few important differences. The rotational orientation of the
relay is continuously variable as the blocks are free to rotate in
the annular recess to adopt a desired relay orientation (leaving
aside the bypass slots where there is no constraint). The annular
recess of course provides little by way of rotational constraint
(in the absence of discrete recess walls which co-operate with the
blocks). Thus the surface of the annular shoulder 29 may be
roughened or textured or otherwise treated so as to mechanically
key or adhere to an upper (co-operating) surface of the blocks 14.
This block surface may itself be roughened, textured or otherwise
treated to enhance the fixing effect. As with the first embodiment
the blocks 14 may have a height which is slightly greater than that
of the annular recess, thereby causing the block to be squeezed
axially by the shoulder 29 when the bracket is tightened onto the
underlying substrate or panel.
In certain aspects the present invention allows a mounting bracket
to be attached to a relay or contactor in a chosen orientation,
regardless of whether the upper end region of the device has
greater bulk or diameter or protrusions or other irregularity which
would prevent the bracket from being pulled down over the upper end
of the device. In addition to allowing the user to select an
optimum mounting orientation/configuration, the combination
provides the option of multiple mounting configurations for
different applications using only one set of components (i.e. one
relay-bracket combination).
In some embodiments, the invention allows the application of a
mounting bracket to fit onto a device with an upper portion having
a larger diameter or cross sectional area than the bracket
aperture. The upper portion of the device may have a regular or
irregular cross sectional shape or profile.
In certain embodiments the bracket has a circular hole the diameter
of which is greater than the diameter of the lower portion of the
device, preferably a sliding fit. The bracket may have slots or
recesses disposed such that they coincide with nubs on the device
when appropriately rotationally oriented.
The bypass slots are open through the thickness (depth) of the
bracket such that the nubs can pass through them without hindrance.
On the underside of the bracket there are recesses, the angular
spacing of which also coincides with the angular spacings
corresponding nubs on the device, but these recesses are blind,
i.e. they do not pass through the entire thickness of the bracket.
The depth of these blind keyways matches, or is slightly less than
the height of the nubs (or blocks) on the device.
It can be seen therefore that the open bypass slots allow the lower
end region of the device to be inserted through the hole in the
bracket. By rotating the bracket the nubs/blocks on the device can
be aligned with any pair of the blind recesses, thus giving
multiple angular relationships between device and bracket.
In another aspect of the invention the plurality of discrete blind
recesses is replaced by a continuous recess on the underside of the
bracket. The depth of this recess would typically be marginally
less than the depth of the nubs/blocks. Thus when the bracket is
tightened down onto the panel, the clamping action of the bracket
onto the nubs/blocks will hold the device secure. The advantage of
this alternative is that there are an unlimited number of positions
of the bracket relative to the device.
The underside of the recess in the bracket and the interfacing top
surface of the nubs/blocks may have a textured surface to provide a
degree of positive mechanical fixing when the bracket is tightened
down onto the mounting plate. Other forms of mechanical fixing or
keying may be provided, such as by the provision of inter-engaging
saw tooth profile elements.
In use the relay body according to certain embodiments or aspects
of the invention as hereinbefore described is introduced to the
bracket and the base end portion of the relay is axially threaded
through the bracket aperture, with the nub or nubs aligned with the
bypass slots. Once the nubs have passed the slots, the relay body
may be rotated with respect to the bracket until a desired relay
body orientation is achieved. In cases where several discrete
recesses (or constraint features) are distributed around the
aperture (or seat) inner surface, the closest discrete recess to
the desired orientation is chosen. In cases where the constraint
feature represents a substantially continuous feature (such as an
annular lip or shoulder) the desired orientation may be adopted
without adjusting to a closest discrete recess. The fixing of the
mounting bracket to an underlying surface or substrate serves to
fix the bracket to the relay (or vice versa) so that the relay is
held in the desired orientation for integration into an electrical
circuit. The use of bypass slots avoids the need for the bracket to
slide over a top (terminal) end of the relay body when engaging
therewith. Hence any terminal end portion shape and configuration
can be used, especially those in which the terminal end portion is
more bulky, or irregular, than the relay body base end portion
which is engaged with the bracket.
In summary, the present invention relates to the field of
electrical relays such as heavy duty relays, also known as
contactors. In particular the invention relates to a bracket a
relay and bracket combination which permits the relay to be mounted
on a surface or panel in a plurality of angular rotational
orientations. There is provided a relay and mounting bracket
combination comprising a relay having a body with a terminal end
portion provided with one or more electrical terminal connectors
and a base end portion adapted for engagement with the bracket,
wherein the bracket is provided with one or more attachment
features which facilitate the mounting of the bracket to an
external object or surface when the bracket is engaged with the
base end portion of the relay, wherein an engagement between the
base end portion and the bracket is made by the co-operation of one
or more protruding nubs with one or more constraint features which
provide axial constraint against withdrawing of the base end
portion from the bracket aperture or seat. The bracket is
preferably provided with a generally annular aperture or seat sized
to accommodate the base end portion therein. The inside surface of
the aperture or recess may be provided with at one or more inwardly
directed shoulder features, sized to accommodate the nub therein
but providing axial constraint which prevents axial withdrawal of
the nub when the shoulder feature covers the nub. The arrangement
is such that the relay base portion may be engaged with the bracket
by aligning the nub or nubs with open axial slots, and then
twisting the bracket with respect to the base portion so that the
nub is accommodated in a shoulder feature, which shoulder feature
blocks disengagement of the base portion from the bracket by acting
upon the constrained nub or nubs.
* * * * *